This implements sending StorageEvents to the same window/doc from where the storage change happened, which seems to be a thing on native IE. For some reason I was unable to have them actually sent to other windows, so that's not implemented since I've no idea how that even gets triggered to test it, and if it does it will probably be in a follow up MR, even though that's *supposed* to be the use of these events���
localStorage sends for `onstoragecommit` on the doc that did the change, while sessionStorage sends for `onstorage` on the window and doc that did the change, depending on compat mode. Although the event sent to the document's `onstorage` seems to be a legacy/old-style event (as tests show).
Tests are on the last patch since events have to be sent properly (else it hangs).
-- v5: mshtml: Send StorageEvents to iframe windows properly. mshtml: Don't expose document.onstorage for IE9+ modes. mshtml/tests: Add tests for StorageEvents with parallel documents. mshtml: Send StorageEvents when removing an existing item. mshtml: Send StorageEvents when setting an item. mshtml: Implement StorageEvent and send it when clearing the storage. mshtml: Move the MessageEvent construction to a helper. include/mshtml: Add IDOMStorageEvent and DispDOMStorageEvent interfaces.